WO2019060480A1

WO2019060480A1 - Cleavage of methyldisilanes, carbodisilanes and methyloligosilanes with alkali-and alkaline earth metal salts

Info

Publication number: WO2019060480A1
Application number: PCT/US2018/051852
Authority: WO
Inventors: Norbert Auner; Tobias SANTOWSKI; Alexander G. STURM
Original assignee: Momentive Performance Materials Inc.
Priority date: 2017-09-20
Filing date: 2018-09-20
Publication date: 2019-03-28

Abstract

The invention relates to a process for the manufacture of methylmonosilanes comprising the step of subjecting one or more methyldisilanes, one or more methyloligosilanes, one or more carbodisilanes, or mixtures thereof to cleavage conditions resulting in the cleavage of silicon- silicon bonds or silicon-carbon bonds in carbodisilanes, and optionally a step of separating the resulting methylmonosilanes.

Description

Cleavage of methyldisilanes, carbodisilanes and methyloligosilanes with alkali- and alkaline earth metal salts TECHNICAL FIELD

The present invention relates to the technical field of the production of methylsilanes, in particular to the production of mono-, di- and trimethylmonosilanes, more specifically to a process for the production of mono-, di- and trimethylsilanes starting from methyldisilanes, and methyloligosilanes by a cleavage reaction of the silicon-silicon bond, and from carbodisilanes by silicon-carbon bond cleavage.

BACKGROUND OF THE INVENTION

Methylchlorosilanes and methylhydridosilanes are highly useful starting materials in synthetic organosilicon chemistry, and therefore constitute an industrially valuable class of compounds. In particular methylsilanes bearing both chloro- and hydrido substituents constitute attractive starting materials in synthesis due to their bifunctional nature, which means they have functional groups of different reactivities. The chloride ligand is a better leaving group than the hydride group and allows, for instance, the controlled addition of further monomeric or oligomeric siloxane units with retention of the Si-H bond under mild conditions, thereby rendering said chlorohydridosilanes useful as blocking and coupling agents in the synthesis of defined oligo- and polysiloxanes.

Such compounds generally find a wide range of applications, for instance for the manufacture of adhesives, sealants, mouldings, composites and resins for example in the fields of electronics, automotive, construction and many more.

The Si-H moieties present in chlorosilanes can be utilized for postsynthesis modifications and functionalisations, for instance for the introduction of organic residues to polyorganosiloxanes or for cross-linking by hydrosilylation reactions, which is desirable in various kinds of compositions containing polyorganosiloxanes.

Synthesis of functionalized polysiloxanes starting with transformations via the Si-H bond(s) followed by hydrolysis or alcoholysis of the Si-CI bond(s) and optionally condensation for the formation of polysiloxanes is also viable. Although there is a high demand for such bifunctional silanes having both Si-H and Si-CI bonds, there is no practical, economically reasonable and sustainable industrial process for the synthesis of such building blocks disclosed yet. The production of methylsilanes by Si-Si-bond cleavage of disilanes has been reported by Lewis and Neely in WO 2013/101618 A1 (US 8,697,901 B2) and WO2013101619A1 (US 8,637,695 B2). In these publications, the hydrochlorinative cleavage of the disilanes of the Direct Process Residue requires the presence of heterocyclic amines or group 15 quarternary onium compounds serving as catalysts. The scope of starting materials in above- cited publications is restricted to perchlorinated methyldisilanes. There is not pointer in these documents to use hydrides or halides/HCI.

In EP 0574912 B1 (B. Pachaly, A. Schinabeck; 1993) a process for the preparation of methylchlorosilanes from the high-boiling residue from the Direct Process by Si-Si-bond cleavage with hydrogen chloride and a catalyst which remains in the reaction mixture, usually a tertiary amine, is described.

In Inorg. Chem. 6, (7) 1967, p.1429-1439 Ring et al. investigated alkali metal salt-catalyzed disproportionation reactions of alkyldisilanes. Therein, only alkali metal hydride or alkali metal deuteride reagents were found to catalyze the disproportionation of monoethyl- and methyldisilane to a silane and a polymer under specific conditions, while LiCI was found to catalyze aforementioned reaction of unsubstituted disilane only. In such document there is no description of the cleavage of chlorodisilanes. Organometallics 1983, 2, 859-864 discloses the disproportionation of disilanes ((MeCI₂Si)₂, Me2CISiSiMeCl2, and (Me2CISi)2) into monomers and a polymer using BU4PCI as catalyst.

J. Organometal. Chem., 9 (1967) 421-426 describes the reaction of LiCH₃ with CH₃Si₂H5. Monatshefte fur Chemie 126, 549-555 (1995), (Hengge et al.) discloses the reaction of 1 ,2- dimethyltetrachlorodisilane (MeSiCl2)2 with tri-n-butyltinhydride (from NaH and tri-n- butyltinchloride) and 1-Methylimidazol in diethylene glycol diethylether.

US 4578495 A describes a process for the preparation of organosilanes and organopolysilanes by contacting, in an inert atmosphere, at least one disilane with a catalyst system comprising an ionic inorganic salt having the formula M⁺A^" and a compound complexing the M⁺ cation. With such process only trace amounts of MeHSiC are obtained.

PROBLEM TO BE SOLVED

The problem to be solved by the present invention is the provision of a process for the production of monosilanes, in particular methylchloro- and methylhydridomonosilanes, by submitting methyldisilanes, methyloligosilanes and carbodisilanes to cleavage conditions, under which the desired products are obtained by Si-Si-bond cleavage or Si-C-bond cleavage in case of carbodisilanes. Further, it is the object of present invention to provide a process with improved product yields, product purity, product selectivity of the conversion, convenience of the work-up procedure, ease of handling of the reagents and cost efficiency of the process. The problem to be solved is in particular the provision of such an improved process in which high proportions of methylhydridomonosilanes and methylhydridochloromonosilanes with a high content of hydride substituents can be obtained.

According to the present invention, this problem is solved as described in the following.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to a process for the production of methylmonosilanes starting from methyldisilanes, carbodisilanes, oligosilanes or mixtures thereof by cleavage of silicon- silicon bonds and of silicon-carbon bonds to methylmonosilanes produced by such process. Aforementioned substrates are constituents of the Direct Process Residue (DPR), a practically inevitable side-product formed in the Rochow-Muller Direct Process. Subject of the invention is a process for the manufacture of methylmonosilanes of the general formula (I):

MexSiHyClz (I), wherein

x = 1 to 3,

y = 0 to 3, preferably 1 to 3,

z = 0 to 3 and

x + y + z = 4, comprising:

A) the step of subjecting a silane substrate comprising one or more silanes selected from the group of a) one or more methyldisilanes of the general formula (I I)

Me_mSi₂H_nClo (I I)

wherein

m = 1 to 6,

n = 0 to 5

o = 0 to 5 and

m + n + o = 6,

b) one or more carbodisilanes of the general formula (II I)

(MeaSiHbCle)-CH2-(Me_cSiHdClf) (I I I)

wherein

a, c are independently of each other 1 to 3,

b, d are independently from each other 0 to 2

e, f are independently from each other 0 to 2,

a + b + e = 3,

c + d + f = 3,

c) one or more linear or branched oligosilanes of the general formula (IV)

MepSiqHrCIs (IV),

wherein

q = 3-7 p = q to (2q + 2)

r, s = 0 to (q + 2)

r + s = (2q + 2) - p

and wherein each Si atom preferably bears at least one methyl group,

or mixtures thereof,

to the cleavage reaction of the silicon-silicon bonds in methyldisilanes of the general formula (II) and oligosilanes of the general formula (IV) as well as cleavage reaction of the silicon- carbon bonds in carbodisilanes of the general formula (III), and

B) optionally a step of separating the resulting methylmonosilanes of the formula (I), wherein step A) is carried out by subjecting the methyldisilanes of the general formula (II), or the carbodisilanes of the general formula (III), or the oligosilanes of the general formula (IV), or the mixtures thereof, to the reaction with at least one compound selected from the group consisting of an alkali metal hydride or alkaline earth metal hydride or mixtures thereof, and optionally hydrogen chloride (HCI), or to the reaction with at least one compound selected from the group consisting of an alkali metal halide, an alkaline earth metal halide and hydrogen chloride.

The methyldisilanes of the general formula (II)

Me_mSi₂H_nClo (II)

can be depicted also by the structural formula:

R' R'

\ /

R'— Si— Si— R'

/ \

R' R' wherein the substituents R' are independently selected from methyl (Me), hydrogen (H) and chlorine (CI), wherein the number of methyl groups m = 1 to 6, the number of hydrogen atoms n = 0 to 5 and the number of chlorine atoms o = 0 to 5, and the total of m + n + o = 6. The carbodisilanes of the general formula (III)

(MeaSiH_bCle)-CH2-(Me_cSiH_dCl_f) (III)

can be depicted also by the structural formula:

wherein the substituents R" are independently selected from methyl (Me), hydrogen (H) and chlorine (CI), and wherein the substituents R'" are independently selected from methyl (Me), hydrogen (H) and chlorine (CI), and

wherein the number of methyl groups on each silicon atom (a, c) is independently from 1 to

3,

wherein the number of hydrogen atoms on each silicon atom (b, d) is independently from 0 to 2, and

wherein the number of chlorine atoms on each silicon atom (e, f) is independently from 0 to 2, preferably e + f > 1.

The linear or branched oligosilanes of the general formula (IV)

MepSiqHrCIs (IV),

are oligosilanes that have a linear or branched silane skeleton, wherein q = 3 to 7 silicon atoms are bonded to each other by single bonds, and the free valencies of the silane skeleton are saturated by substituents selected from methyl (Me), hydrogen (H) and chlorine (CI) with the proviso that the number of methyl groups p = q to (2q + 2), which corresponds to the case where each silicon atom has one methyl group (p=q) and the case of permethylated silanes (p= 2q+2) and which means that there are at least 3 methyl groups up to 16 methyl groups (i.e. in Si₇Mei₆) in the silanes; and the number of hydrogen atoms (r) and chlorine atoms (s) are independently of each other 0 to (q + 2), and r + s = (2q + 2) - p, wherein q is the number of silicone atoms and p is the number of methyl groups, again with the preferred proviso that each Si atom bears at least one methyl group. Preferably s is > 1.

In a preferred embodiment of the invention the silane substrate is consisting of one or more compounds represented by general formulae (II), (III), or (IV). In the process of the present invention, one compound of general formula (I) or a mixture of more than one compounds of general formula (I) is formed. More preferably, mixtures of more than one compound of the formula (I) are formed. Preferably hydridomonosilanes are formed wherein y = 1 to 3, more preferably y = 1 or 2.

Further preferably, the methylmonosilanes of the general formula (I) formed in the process of the present invention include compounds selected from the group of: MeSiH₂CI, Me₂SiH₂, Me₂SiHCI, Me₃SiH, Me₃SiCI, MeSiHCI₂, Me₂SiCI₂, MeSiC and MeSiH₃. Even more preferably, the methylmonosilanes of the general formula (I) formed in the process according to the invention include compounds selected from the group of Me₂SiH₂, Me₂SiHCI, MeSiH₂CI, MeSiHCI₂ and MeSiH₃. Most preferred are Me₂SiHCI, MeSiH₂CI, and MeSiHCI₂. The one or more methyldisilanes subjected to the cleavage reaction of the silicon-silicon bond are represented by the general formula (II), wherein m = 1 to 6, preferably m = 2 to 6.

More preferably, the methyldisilanes subjected to the cleavage reaction of the silicon-silicon bond are represented by the general formula (II) with m = 2 to 6, wherein n = 0. Such constituents of the Direct Process Residue (DPR) from the Rochow-Muller Direct Synthesis, for example the methyldisilanes Me₃Si-SiMe₂CI, CIMe₂Si-SiMe₂CI, CI₂MeSi-SiMeCI₂, CIMe₂Si-SiMeCI₂, Me₃Si-SiMeCI₂, are therefore preferred substrates in the process according to the invention. The one or more carbodisilanes subjected to the cleavage reaction of one or both carbon- silicon bonds which connect the silyl groups to the methylene group linking the silyl groups of the compounds are represented by the general formula (III).

Herein, it is preferred that b = d = 0, as such substrates, in particular Me₃Si-CH₂-SiMe₂CI, CIMe₂Si-CH₂-SiMe₂CI, CI₂MeSi-CH₂-SiMeCI₂, CIMe₂Si-CH₂-SiMeCI₂ and Me₃Si-CH₂-SiMeCI₂ may be constituents of the Direct Process Residue (DPR).

The one or more linear or branched oligosilanes subjected to the cleavage reaction of the silicon-silicon bonds are represented by the general formula (IV).

Herein, it is preferred that r = 0, as such substrates, in particular CIMe₂Si-SiMe₂-SiMe₂CI, CIMe₂Si-SiMe₂-SiMe₂-SiMe₂CI, (CIMe₂Si)₃SiMe, (CI₂MeSi)₂SiMeCI, (CI₂MeSi)₃SiMe, (CI₂MeSi)₂SiMe-SiCIMe-SiCI₂Me, [(CI₂MeSi)₂SiMe]₂, [(CI₂MeSi)₂SiMe]₂SiCIMe and (CI₂MeSi)₂SiMe-SiMe₂CI, may be constituents of the Direct Process Residue.

The substrates according to the general formulae (II), (III) and (IV) may be submitted to the conditions for cleavage reactions in step A) as single compounds represented by general formulae (II), (III) and (IV), as a mixture of compounds represented by general formulae (II), (II I) and (IV), or as mixtures comprising one or more compounds represented by general formulae (II), (III), or (IV). Therein, cleavage is the term used to describe the transformation by which disilanes represented by the general formula (II), carbodisilanes represented by the general formula (II I) and oligosilanes represented by the general formula (IV) are reacted to produce monomeric silanes represented by the general formula (I). In the case of disilanes of the general formula (II) and oligosilanes of the general formula (IV), the term "cleavage reaction of the silicon-silicon bonds" further indicates that according to the invention, the cleavage of the aforementioned substrates is effected by breaking the bond connecting the silicon atoms of these disilanes and oligosilanes. In the case of carbodisilanes of the general formula (III), the term "cleavage reaction of the silicon-carbon bonds" indicates that the cleavage reaction is effected by breaking one or both bonds between the silyl groups of the compounds and the methylene group linking the silyl groups. Such cleavage processes comprise in particular hydrochlorination and hydrogenolysis reactions.

The optional step of separating the resulting methylmonosilanes of the general formula (I) refers to any technical means applied to raise the content of one or more methylmonosilanes according to the general formula (I) in a product mixture, or which results in the separation of single compounds of the formula (I) from a product mixture obtained in step A) of the process according to the invention.

In a preferred embodiment of the process according to the invention, the starting materials of the general formulae (II), (III) and (IV) do not bear hydrogen substituents, which means that in the disilanes of the general formula (II) n = 0, in the carbodisilanes of the general formula (II I) b and d = 0, and in the oligosilanes of the general formula (IV), r = 0.

The substrate according to this embodiment are typically found as constituents of the Direct Process Residue. In the process of the invention, step A) is carried out by subjecting the methyldisilanes of the general formula (II), or the carbodisilanes of the general formula (III), or the oligosilanes of the general formula (IV), or the mixtures thereof, to the reaction with at least one compound selected from the group consisting of an alkali metal hydride or alkaline earth metal hydride or mixtures thereof, and optionally hydrogen chloride (HCI), or to the reaction with at least one compound selected from the group consisting of an alkali metal halide, an alkaline earth metal halide and hydrogen chloride.

Preferably the alkali metal halides and alkaline earth metal halides are bromide, fluoride or chloride salts, more preferably fluoride or chloride salts, and most preferably chloride salts. A general trend in reactivity of metal halide salts in the cleavage reactions of the process according to the invention is that chloride salts are more reactive than fluoride salts, while bromide salts are least reactive. In a more preferred embodiment of the process according to the invention, step A) is carried out by subjecting the methyldisilanes of the general formula (II), or the carbodisilanes of the general formula (III), or the oligosilanes of the general formula (IV), or the mixtures thereof, to the reaction with at least one compound selected from the group consisting of lithium hydride, sodium hydride, potassium hydride, magnesium hydride, and calcium hydride and mixtures thereof.

In a more preferred embodiment of the process according to the invention, step A) is carried out by subjecting the methyldisilanes of the general formula (II), or the carbodisilanes of the general formula (III), or the oligosilanes of the general formula (IV), or the mixtures thereof, to the reaction with at least one compound selected from the group consisting of lithium chloride, sodium chloride, potassium chloride, magnesium chloride, calcium chloride, lithium fluoride, sodium fluoride, potassium fluoride, magnesium fluoride, calcium fluoride, lithium bromide, sodium bromide, potassium bromide, magnesium bromide, calcium bromide and mixtures thereof, and hydrogen chloride.

In a further preferred embodiment of the process according to the invention, step A) is carried out by subjecting the methyldisilanes of the general formula (II), or the carbodisilanes of the general formula (III), or the oligosilanes of the general formula (IV), or the mixtures thereof to the reaction with at least one compound selected from the group consisting of lithium hydride, sodium hydride, calcium hydride and mixtures thereof, and optionally hydrogen chloride. In a further preferred embodiment of the process according to the invention, step A) is carried out by subjecting the methyldisilanes of the general formula (II), or the carbodisilanes of the general formula (III), or the oligosilanes of the general formula (IV), or the mixtures thereof to the reaction with at least one compound selected from the group consisting of lithium chloride, sodium chloride, potassium chloride, and mixtures thereof, and hydrogen chloride.

In another preferred embodiment of the process according to the invention, step A) is carried out by subjecting the methyldisilanes of the general formula (II), or the carbodisilanes of the general formula (III), or the oligosilanes of the general formula (IV), or the mixtures thereof to the reaction with at least one compound selected from lithium hydride, sodium hydride, a mixture of sodium hydride or calcium hydride and lithium chloride, and optionally hydrogen chloride.

In another preferred embodiment of the process according to the invention, step A) is carried out by subjecting the methyldisilanes of the general formula (II), or the carbodisilanes of the general formula (III), or the oligosilanes of the general formula (IV), or the mixtures thereof to the reaction with at least one compound selected from lithium chloride and potassium chloride, and hydrogen chloride.

In a further preferred embodiment of the process according to the invention, step A) is carried out by subjecting the methyldisilanes of the general formula (II), or the carbodisilanes of the general formula (III), or the oligosilanes of the general formula (IV), or the mixtures thereof to the reaction with lithium hydride, or a combination of lithium hydride and lithium chloride, and optionally hydrogen chloride.

In a further preferred embodiment of the process according to the invention, step A) is carried out by subjecting the methyldisilanes of the general formula (II), or the carbodisilanes of the general formula (III), or the oligosilanes of the general formula (IV), or the mixtures thereof to the reaction with lithium chloride and hydrogen chloride.

In a further preferred embodiment of the process according to the invention, step A) is carried out by subjecting the methyldisilanes of the general formula (II), or the carbodisilanes of the general formula (III), or the oligosilanes of the general formula (IV), or the mixtures thereof to the reaction with lithium hydride, or lithium chloride and hydrogen chloride, or a mixture of sodium hydride or calcium hydride and lithium chloride.

In a further preferred embodiment of the process according to the invention, step A) is carried out in the presence of at least one compound (sometimes referred to as "cleavage compound") selected from the group consisting of

- a quaternary Group 15 onium compound R₄QX, wherein each R is independently a hydrogen or an organyl group, Q is phosphorus, arsenic, antimony or bismuth, and X is a halide selected from the group consisting of F, CI, Br and I ,

- heterocyclic amines and heterocyclic ammonium halides,

and mixtures of the above-mentioned compounds.

Preferably the quaternary Group 15 onium compound is represented by the formula R₄PCI, wherein R is independently a hydrogen group or an organyl group, more preferably a hydrogen group, an aromatic group or an aliphatic hydrocarbon group, preferably having up to 10 carbon atoms. The compounds of formula R₄PCI can be also formed in situ from compounds of formula R₃P and RCI.

In a preferred embodiment of the process of the invention the molar ratio of the cleavage compound used in step A) to the silane substrate compounds of the general formulae (I I) , (II I) and (IV) is in the range of about 0.0001 to about 4 mol-% , more preferred about 0.001 to about 0.5 mol-%, even more preferred about 0.01 to about 0.2 mol-%, and most preferably about 0.01 to about 0.1 mol-% based on the molar amount of the silane substrate compounds.

In a preferred embodiment of the process of the invention the weight ratio of the cleavage compound used in step A) to the silane substrate is in the range of about 0.01 to about 99.95 wt-%, more preferred about 0.1 to about 55 wt-% , even more preferred about 1 to about 25 wt-% and most preferably about 2 to about 10 wt-%, wherein the weight percentage wt-% is based on the total weight of the silane substrate.

In a particular preferred embodiment of the process of the invention step A) is carried out in the presence of at least one compound of the formula R₄PCI, preferably in the presence of at least one compound of the formula R PCI and at least one methylimidazole. Most preferred the cleavage compound used in step A) is n-Bu₄PCI, preferably a mixture of n-Bu₄PCI and 2- methylimidazole.

In a preferred embodiment of the process of the invention the step A) is carried out in the presence of at least one compound of the formula R₄PCI and at least one metal hydride, preferably lithium hydride (LiH), more preferably in the presence of n-Bu₄PCI and lithium hydride. Preferably step A) is carried out in the presence of about 0.5 to about 25 weight-% n-Bu4PCI wherein the weight percentage wt-% is based on the total weight of the silane substrate and about 25 to about 75 mol-% LiH based on the total molar amount of the chlorine atoms present in silane substrate compounds.

In a preferred embodiment of the process of the invention the step A) is carried out in the presence of at least one cleavage compound selected from quaternary Group 15 onium compounds represented by the formula R₄QX, wherein each R is independently a hydrogen or an organyl group, Q is phosphorus, arsenic, antimony or bismuth, and X is a halide selected from the group consisting of F, CI, Br and I , at a temperature of about 0 °C to about 300 °C, more preferably about 20 °C to about 220 °C, and even more preferably at about 80 to about 160 °C. Preferably step A) is carried out using at least one cleavage compound selected from heterocyclic amines and heterocyclic ammonium halides, at a temperature of about 0 °C to about 300 °C, more preferably about 20 °C to about 220 °C, even more preferably at about 100 to about 220 °C, and most preferably at about 140 °C to about 220 °C. In another preferred embodiment of the process of the invention the step A) is carried out in the presence of at least one cleavage compound selected from quaternary Group 15 onium compounds represented by the formula R4QX, wherein each R is independently a hydrogen or an organyl group, Q is phosphorus, arsenic, antimony or bismuth, and X is a halide selected from the group consisting of F, CI, Br and I, and at least one cleavage compound selected from heterocyclic amines and heterocyclic ammonium halides, at a temperature of about 0 °C to about 300 °C, more preferably about 50 °C to about 220 °C, even more preferably at about 100 to about 200 °C, and most preferably at about 120 °C to about 180 °C.

In a preferred embodiment of the process according to the invention, before, during or after the cleavage reaction of the substrates of the general formulae (II), (III) and (IV), also a hydrogenation reaction of the substrates or the products of the general formula (I) takes place under the reaction conditions of step A).

In the sense of the present invention, the term "hydrogenation" refers to the exchange of at least one chloro substituent of a compound by a hydrogen substituent by means of a hydride reagent.

Preferably, one or more chloro substituents of at least one or more compounds of the general formulae (II), (III) or (IV) submitted to the reaction conditions of step A) are replaced by hydrogen substituents before or during the cleavage reaction. Also preferably, one or more chloro substituents of at least one or more monosilanes of the general formula (I) obtained in step A) or being part of the substrate mixture are replaced by hydrogen substituents before, during or after the cleavage reaction in step A) .

By such hydrogenation reactions, the ratio of hydrogen substituents to chloro substituents in the products of the general formula (I) is increased.

In a preferred embodiment of the process according to the invention, step A) is carried out in the presence of an organic solvent.

In the sense of present invention, an organic solvent is any organic compound which is in liquid state at room temperature, and which is suitable as a medium for conducting the cleavage reactions therein. Accordingly, the organic solvent is preferably inert to the hydride donors according to present invention, to alkaline earth metal halides and to alkali metal halides under reaction conditions. Furthermore, the starting materials of the general formulae (II), (I I I) and (IV) and the products of the general formula (I) are preferably soluble in the organic solvent or fully miscible, respectively.

Preferably, the organic solvent is selected from optionally substituted, preferably unsubstituted linear or cyclic aliphatic hydrocarbons, aromatic hydrocarbons or ether compounds, without being limited thereto.

In a more preferred embodiment of the process according to the invention, step A) is carried out in the presence of an organic solvent, wherein said organic solvent is selected from one or more ether compounds.

According to the present invention, the ether compound is preferably selected from the group consisting of linear and cyclic aliphatic ether compounds. In the present invention, the term "ether compound" shall mean any organic compound containing an ether group -0-, in particular of formula R1-O-R2, wherein Ri and R2, are independently selected from an organyl group R.

The organyl group R is selected from optionally substituted, preferably unsubstituted, alkyl, aryl, alkenyl, alkynyl, alkaryl, aralkyl, aralkenyl, aralkynyl, cycloalkyl, cycloalkenyl, cycloalkynyl, cycloaralkyi, cycloaralkenyl, cycloaralkynyl, alkoxy, aryloxy, and organosiloxy (cyclic and acyclic) groups, preferably alkyl, alkenyl and aryl groups. Preferably, Ri and R₂, are substituted or unsubstituted linear or branched alkyl groups or aryl groups, which may have further heteroatoms such as oxygen, nitrogen, or sulfur. In the case of cyclic ether compounds, Ri and R₂ can constitute together an optionally substituted alkylene or arylene group, which may have further heteroatoms such as oxygen, nitrogen, or sulfur.

The ether compounds can be symmetrical or asymmetrical with respect to the substituents at the ether group -0-.

In another preferred embodiment of the process of the present invention, the organic solvent in which step A) is conducted is a mixture of one or more ether compounds and one or more non-ether compounds.

Preferably, the one or more non-ether compounds forming the mixture with one or more ether compounds are selected from solvents which are less polar than the ether compounds used, particular preferably from aliphatic or aromatic hydrocarbons.

In a further preferred embodiment of the process according to the invention, the ether compounds in which step A) is conducted or which are a part of the solvent mixture in which step A) is conducted, are selected from the group of linear, cyclic or complexing ether compounds.

Herein, a linear ether compound is a compound containing an ether group R1-O-R2 as defined above, in which there is no connection between the Ri and R₂ group except the oxygen atom of the ether group, as for example in the symmetrical ethers Et₂0, n-Bu₂0, Ph₂0 or diisoamyl ether (/-Penty O), in which Ri = R₂, or in unsymmetrical ethers as t- BuOMe (methyl f-butyl ether, MTBE) or PhOMe (methyl phenyl ether, anisol).

A cyclic ether compound according to the invention is a compound in which one or more ether groups are included in a ring formed by a series of atoms, such as for instance tetrahydrofuran, tetrahydropyran or 1 ,4-dioxane, which can be substituted e.g. by alkyl groups.

In linear ether compounds, also more than one ether group may be included forming a di- , tri-, oligo- or polyether compound, wherein Ri and R₂ constitute organyl groups when they are terminal groups of the compounds, and alkylene or arylene groups when they are internal groups. Herein, a terminal group is defined as any group being linked to one oxygen atom which is part of an ether group, while an internal group is defined as any group linked to two oxygen atoms being a constituent of ether groups.

Preferred examples of such compounds are dimethoxy ethane, glycol diethers (glymes) , in particular diglyme or tetraglyme, without being limited thereto.

In the sense of present invention, the term "complex ether" is understood as an ether compound as defined above which is capable of complexing cations, preferably metal cations, more preferably alkali and alkaline metal cations, even more preferably alkaline metal cations, and most preferably lithium cations. Preferred examples of such complex ethers according to the invention are glycol diethers (glymes), in particular diglyme, triglyme, tetraglyme or pentaglyme, or crown ethers, in particular 12-crown-4, 15-crown-5, 18-crown-6, dibenzo- 18-crown-6, and diaza-18-crown-6 without being limited thereto.

The term "complexing ether" is understood equivalently to the term "complex ether".

In another preferred embodiment of the process according to the invention, the ether compound is selected from the group consisting of linear ethers, such as diethyl ether, di-n-butyl ether, complexing ethers, such as dimethoxy ethane, diethylene glycol dimethyl ether (diglyme) or tetraethylene glycoldimethyl ether (tetraglyme) , alkylated polyethylene glycols (alkylated PEGs) , cyclic ethers such as dioxane, preferably 1 ,4-dioxane, 2- methyltetrahydrofuran, tetrahydrofuran, or tetrahydropyran.

In a particularly preferred embodiment of the process according to the invention, the ether compound is a high-boiling ether compound, most preferably diglyme or tetraglyme.

According to the present invention, the term "high-boiling ether compound" is defined as an ether compound according to above definition with a boiling point at 1 bar (ambient pressure) of preferably at least about 70 °C, more preferably at least about 85 °C, even more preferably at least about 100 °C, and most preferably at least about 120 °C.

The application of high-boiling ethers in the present invention is favorable as it facilitates separation of the desired products of the general formula (I) from the reaction mixture containing the solvent and residual starting materials. The products of the general formula (I) in general have lower boiling points than the starting materials, and the boiling points of these products are also lower than the boiling point of high-boiling ethers of above definition. For instance, the boilings point (at normal pressure 1 atm) of selected representative products of the general formula (I) are about 35 °C (Me₂SiHCI), about 41 °C (MeSiHC ) or about 66 °C (MeSiC ), while representative higher-boiling ether compound diglyme has a boiling point of about 162 °C, and the boiling point of a mixture of methylchlorodisilanes principally consisting of isomers of trimethyltrichlorodisilane and dimethyltetrachlorodisilanes, which are respective substrates of the general formula (I I) is about 151 to about 158 °C. Application of higher-boiling ether compounds as solvents allows to utilize higher reaction temperatures and simplifies separation of the desired products from the reaction mixture by distillation.

In a preferred embodiment of the process according to the invention, step A) is conducted at a temperature of about 0 °C to about 220 °C, preferably about 20 °C to about 180 °C, more preferably about 20 °C to about 140 °C, most preferably about 60 °C to about 140 °C. Herein, the reaction temperature in step A) according to the invention is the temperature of the reaction mixture, i.e. the temperature measured inside the reaction vessel in which the reaction is conducted.

Preferably, the reaction vessel can be an ampoule, a sealed tube, a flask or any kind of chemical reactor, without being limited thereto.

Further preferably, the reaction step A) is carried out in a suitably sized reactor made of materials, such as glass or Hastelloy C, which are resistant to corrosion by chlorides. A means of vigorous agitation is provided to disperse the metal hydride or halide in the solvent.

In a further preferred embodiment of the process according to the invention, step A) is conducted at a pressure of about 0.1 bar to about 30 bar, preferably about 1 bar to about 20 bar, most preferably about 1 bar to about 10 bar. The indicated pressure ranges refer to the pressure measured inside the reaction vessel used when conducting reaction step A).

In a preferred embodiment of the process according to the present invention, in step A) the weight ratio of the methyldisilanes of the general formula (II), the carbodisilanes of the general formula (III), the oligosilanes of the general formula (IV) or mixtures thereof to the organic solvent is less than about 4: 1 , preferably in the range of about 2: 1 to about 1 : 1 , more preferably about 1 :2 to about 1 :20.

Herein, the weight ratio is defined as m (methyldisilanes of the general formula (II), carbodisilanes of the general formula (II I), oligosilanes of the general formula (IV))/ m (organic solvent).

For the determination of this ratio, all compounds being methyldisilanes of the general formula (II), carbodisilanes of the general formula (II I) and oligosilanes of the general formula (IV) submitted to the reaction step (A) are considered, regardless if they are submitted as a part of a mixture comprising other compounds, in particular disilanes and carbodisilanes, which do not fall under the general formulae (I I), (III) or (IV). Furthermore, the mass of any organic solvent according to above definition of the term "organic solvent" present in the reaction mixture submitted to reaction step (A) is considered in the determination of the weight ratio.

In another preferred embodiment of the process according to the invention, the molar ratio of hydride anions stemming from the at least one compound selected from the group consisting of an alkali metal hydride or alkaline earth metal hydride or mixtures thereof, to the chlorine atoms present in the methyldisilanes of the general formula (II), the carbodisilanes (I II), or the oligosilanes of the general formula (IV), or mixtures thereof is in the range of about 1 to about 600 mol-%, more preferred about 25 to about 400 mol-%, even more preferred about 25 to about 200 mol-%, and most preferred about 25 to about 100 mol-%.

Herein, the molar ratio is defined as n (hydride anions contained in the compound or compounds used as cleavage reagent in step A)) / n(chlorine atoms contained in the substrates of the general formulae (II), (III) and (IV) ).

For the determination of this ratio, all compounds being methyldisilanes of the general formula (II), carbodisilanes of the general formula (II I) and oligosilanes of the general formula (IV) submitted to the reaction step (A) are considered, regardless if they are submitted as a part of a mixture comprising other compounds, in particular disilanes and carbodisilanes, which do not fall under the general formulae (II), (III) or (IV). In a further preferred embodiment of the process according to the invention, the molar ratio of halide anions stemming from the at least one compound selected from the group consisting of an alkali metal halide or alkaline earth metal halide or mixtures thereof, to the methyldisilanes of the general formula (II), the carbodisilanes (III) or the oligosilanes of the general formula (IV), or mixtures thereof is in the range of about 1 to about 600 mol-%, more preferred about 25 to about 400 mol-%, even more preferred about 25 to about 200 mol-%, and most preferred about 25 to about 100 mol-%.

Herein, the molar ratio is defined as

n (halide anions contained in the least one compound selected from the group consisting of an alkali metal halide or alkaline earth metal halide or mixtures thereof, applied in step A)) / n (substrate compounds of the general formulae (I I), (III) and (IV) ).

For the determination of this ratio, all compounds being methyldisilanes of the general formula (II), carbodisilanes of the general formula (II I) and oligosilanes of the general formula (IV) submitted to the reaction step (A) are considered, regardless if they are submitted as a part of a mixture comprising other compounds, in particular disilanes and carbodisilanes, which do not fall under the general formulae (II), (III) or (IV). In another preferred embodiment of the process according to the invention, the molar ratio of lithium chloride to the methyldisilanes of the general formula (I I), the carbodisilanes (III), or the oligosilanes of the general formula (IV) or mixtures thereof is in the range of 1 to 600 mol- %, more preferred about 25 to about 400 mol-%, even more preferred about 25 to about 100 mol-%, and most preferred about 25 to about 50 mol-%.

Herein, the molar ratio is defined as n (lithium chloride applied in step A) ) / n (substrate compounds of the general formulae (II),

(II I) and (IV) ).

For the determination of this ratio, all compounds being methyldisilanes of the general formula (II), carbodisilanes of the general formula (II I) and oligosilanes of the general formula

(IV) submitted to the reaction step (A) are considered, regardless if they are submitted as a part of a mixture comprising other compounds, in particular disilanes and carbodisilanes, which do not fall under the general formulae (II), (III) or (IV). In a preferred embodiment of the process according to the invention, the molar concentration of the at least one compound selected from the group consisting of an alkali metal halide, an alkaline earth metal halide, an alkali metal hydride or alkaline earth metal hydride or mixtures thereof, used for cleavage is in the range of about 0.0001 to about 15 mol/l, more preferred about 0.05 to about 10 mol/l, even more preferred about 0.5 to 5 mol/l, and most preferred about 0.5 to about 3 mol/l based on the volume of the reaction mixture in step A).

In a further preferred embodiment of the process according to the invention, step A) is conducted in the presence of HCI.

In the presence of HCI only diminished or no formation of oligosilanes occurs. By this, the yield of products of the general formula (I) in the process according to the invention can be improved. HCI acts as a silylene trapping agent and prevents silylenes formed from inserting into the Si-Si-bond to build up oligomeric structures.

In another preferred embodiment of the process according to the invention, step A) is conducted in the presence of HCI and LiCI or HCI and KCI.

Herein, lithium chloride can be added directly to the reaction mixture, or it can be formed in- situ from the reaction, for instance with lithium hydride and chlorodisilanes to give LiCI and hydridosilanes, likewise potassium chloride can be added directly to the reaction mixture, or it can be formed in situ from the reaction.

In still another preferred embodiment of the process according to the invention, the molar ratio of the methyldisilanes of the general formula (II), or the carbodisilanes of the general formula (III), or the oligosilanes of the general formula (IV), or the mixtures thereof to HCI is about 0.2 to about 5, more preferably about 0.5 to about 2, even more preferably about 0.75 to about 1 .25, and most preferably about 1 : 1 . Herein, the molar ratio is defined as

n (substrate compounds of the general formulae (II), (III) and (IV)) / n (HCI applied in step A) ).

For the determination of this ratio, all substrate compounds of the general formulae (II), (I II) and (IV) submitted to the reaction step (A) are considered, regardless if they are submitted as a part of a mixture comprising other compounds, in particular disilanes and carbodisilanes, which do not fall under the general formulae (II), (II I) or (IV).

In a preferred embodiment of the process according to the invention, step A) is carried out in diglyme or tetraglyme as solvent.

Diglyme and tetraglyme are preferably applied as solvents in the present invention due to their favourable properties for the process such as relatively high boiling points, high abilities to dissolve alkali metal and alkaline earth metal salts, in particular lithium salts, and beneficial effects on reaction rates.

In another preferred embodiment of the process according to the present invention, the methyldisilanes of the general formula (II), or the carbodisilanes of the general formula (III), or the oligosilanes of the general formula (IV), or the mixtures thereof are residues of the Rochow-Muller Direct Process, so-called Direct Process Residue (DPR).

The primary commercial method to prepare alkylhalosilanes and arylhalosilanes is through the Rochow-Muller Direct Process (also called Direct Synthesis or Direct Reaction), in which copper-activated silicon is reacted with the corresponding organohalide, in particular methyl chloride, in a gas-solid or slurry-phase reactor. Gaseous products and unreacted organohalide, along with fine particulates, are continuously removed from the reactor. Hot effluent exiting from the reactor comprises a mixture of copper, metal halides, silicon, silicides, carbon, gaseous organohalide, organohalosilanes, organohalodisilanes, carbosilanes and hydrocarbons. Typically, this mixture is first subjected to gas-solid separation in cyclones and filters. Then the gaseous mixture and ultrafine solids are condensed in a settler or slurry tank from which the organohalide, organohalosilanes, hydrocarbons and a portion of organohalodisilanes and carbosilanes are evaporated and sent to fractional distillation to recover the organohalosilane monomers. The solids accumulated in the settler along with the less volatile silicon-containing compounds are purged periodically and sent to waste disposal or to secondary treatment. Organohalodisilanes and carbosilanes left in the post-distillation residues are also fed to hydrochlorination. Organohalodisilanes, organohalopolysilanes and carbosilanes, related siloxanes and hydrocarbons, either in the post-distillation residues or in the slurry purged from the reactor, boil above organohalosilane monomers. Collectively they are referred to as Direct Process Residue (DPR). The terms higher boilers, high-boiling residue and disilane fraction are also used interchangeably with DPR. By the process according to the invention, methylchlorodisilanes of the general formula (I I), carbodisilanes of the general formula (II I) and oligosilanes of the general formula (IV), which are constituents of the side-products of the Rochow-Muller Direct Process (DPR) can be transformed to monosilanes of the general formula (I) via cleavage reactions and optionally hydrogenation of the substrates of the formulae (II), (I II), and (IV) or the products (I),

According to the invention, the Direct Process Residue (DPR) utilized as starting material may comprise further silicon-based compounds which do not fall under the general formulae (II), (III) and (IV).

In a further preferred embodiment of the process according to the invention the methylmonosilanes of the general formula (I) are selected from the group consisting of MeSiCb, Me₂SiHCI, MeSiH₂CI, MeSiHCI₂, Me₃SiCI, Me₃SiH, MeSih and Me₂SiCI₂, Me₂SiH₂, or mixtures thereof.

In a particularly preferred embodiment of the process of the invention, the methylmonosilanes of the formula (I) are selected from the group consisting of Me₂SiHCI, MeSiH₂CI and MeSiHC , or mixtures thereof. In a preferred embodiment of the process according to the invention, dimethylchloromonosilane Me₂SiHCI is formed by submitting a substrate comprising one or more silanes selected from the group consisting of CIMe₂Si-SiMe₂CI, CIMe₂Si-SiMeCI₂, Me₃Si-SiMe₂CI, HMe₂Si-SiMe₂H, HMe₂Si-SiMeH₂, Me₃Si-SiMe₂H, CIMe₂Si-SiMe₂H, CIMe₂Si- SiMeH₂, HMe₂Si-SiMeCI_2, CIMe₂Si-CH₂-SiMeCI₂, CIMe₂Si-CH₂-SiMe₂CI, Me₃Si-CH₂-SiMe₂CI, CIMe₂Si-SiMe₂-SiMe₂CI, CIMe₂Si-SiMe₂-SiMe₂-SiMe₂CI and (CIMe₂Si)₃SiMe to the cleavage reactions of step A).

Therein, each of the above-stated substrates may be submitted to the reaction conditions as single substrate, in a mixture with other compounds of the above-stated compounds, or in a mixture with other substrates of the general formulae (II), (III) or (IV).

In another preferred embodiment of the process according to the invention, methylchloromonosilane MeSiH₂CI is formed by submitting a substrate comprising one or more silanes selected from the group consisting CI₂MeSi-SiMeCI₂, CI₂MeSi-SiMe₂CI, CI₂MeSi-SiMe₃, H₂MeSi-SiMeH₂, H₂MeSi-SiMe₂H, H₂MeSi-SiMe₃, HCIMeSi-SiMeH₂, HCIMeSi-SiMeCIH, HCIMeSi-SiMeCI₂, CI₂MeSi-SiMeH₂, CIHMeSi-SiMe₂CI, CI₂MeSi-SiMe₂H, CIHMeSi-SiMe₂H, H₂MeSi-SiMe₂CI, CI₂MeSi-CH₂-SiMeCI₂, CIMe₂Si-CH₂-SiMeCI₂, Me₃Si- Chb-SiMeCh, (CI₂MeSi)₂SiMeCI, (CI₂MeSi)₃SiMe, (CI₂MeSi)₂SiMe-SiCIMe-SiCI₂Me, [(CI₂MeSi)₂SiMe]₂, [(CI₂MeSi)₂SiMe]₂SiCIMe and (CI₂MeSi)₂SiMe-SiMe₂CI to the cleavage reactions of step A).

In a further preferred embodiment of the process according to the invention, methyldichloromonosilane MeSiHCI₂ is formed by submitting a substrate comprising one or more silanes selected from the group consisting of CI₂MeSi-SiMeCI₂, CI₂MeSi-SiMe₂CI, CI₂MeSi-SiMe₃, HCIMeSi-SiMeH₂, HCIMeSi-SiMeCIH, HCIMeSi-SiMeCI₂, CI₂MeSi-SiMeH₂, CIHMeSi-SiMe₂CI, CI₂MeSi-SiMe₂H, CIHMeSi-SiMe₂H, H₂MeSi-SiMe₂CI, CI₂MeSi-CH₂- SiMeCI₂, CIMe₂Si-CH₂-SiMeCI₂, Me₃Si-CH₂-SiMeCI₂, (CI₂MeSi)₂SiMeCI, (CI₂MeSi)₃SiMe, (CI₂MeSi)₂SiMe-SiCIMe-SiCI₂Me, [(CI₂MeSi)₂SiMe]₂, [(CI₂MeSi)₂SiMe]₂SiCIMe and (CI₂MeSi)₂SiMe-SiMe₂CI to the cleavage reactions of step A).

Therein, each of the above-stated substrates may be submitted to the reaction conditions as single substrate, in a mixture with other compounds of the above-stated compounds, or in a mixture with other substrates of the general formula (II), (III) or (IV). In a preferred embodiment of the process according to the invention, step B) of separating the resulting methylmonosilanes of the formula (I) is carried out by condensation, distillation or a combination thereof.

The term "distillation" in the sense of the present invention relates to any process for separating components or substances from a liquid mixture by selective evaporation and condensation. Therein, distillation may result in practically complete separation of the constituents of a mixture, thus leading to the isolation of nearly pure compounds, or it may be a partial separation that increases the concentration of selected constituents of the mixture in the distillate when compared to the mixture submitted to distillation.

Preferably, the distillation processes which may constitute separation step B) can be simple distillation, fractional distillation, vacuum distillation, short path distillation or any other kind of distillation known to the skilled person. Also preferably, the step B) of separating the monosilanes of the formula (I) according to the invention can comprise one or more batch distillation steps, or can comprise a continuous distillation process. Further preferably, the term "condensation" may comprise separation or enrichment of one or more compounds of the general formula (I I) from the reaction mixture by volatilization from the reaction vessel and condensation as a liquid and/or solid in a refrigerated vessel from which it can be subsequently recovered by distillation, or by solution in an ether solvent. Alternatively, the hydridosilane can be absorbed in an ether solvent contained in a refrigerated vessel.

In another preferred embodiment of the process according to the invention, the step B) of separating the resulting methylmonosilanes of the formula (I) is carried out by distillation. In still another preferred embodiment of the process according to the invention, the process is carried out under inert conditions.

In the sense of present invention, the term "performed under inert conditions" means that the process is partially or completely carried out under the exclusion of surrounding air, in particular of moisture and oxygen. In order to exclude ambient air from the reaction mixture and the reaction products, closed reaction vessels, reduced pressure and/or inert gases, in particular nitrogen or argon, or combinations of such means may be used.

Preferred embodiments of the invention:

In the following the preferred embodiments of the invention are shown:

1. Process for the manufacture of methylmonosilanes of the general formula (I):

MexSiHyClz (I), wherein

x = 1 to 3,

y = 0 to 3, preferably 1 to 3,

z = 0 to 3 and

x + y + z = 4,

comprising:

A) the step of subjecting a silane substrate comprising one or more silanes selected from the group of

a) one or more methyldisilanes of the general formula (II)

Me_mSi₂H_nClo (II)

wherein

m = 1 to 6,

n = 0 to 5

o = 1 to 5 and

m + n + o = 6,

b) one or more carbodisilanes of the general formula (III)

(MeaSiH_bCle)-CH2-(Me_cSiH_dCl_f) (III)

wherein

a, c are independently of each other 1 to 3, b, d are independently from each other 0 to 2

e, f are independently from each other 0 to 2,

a + b + e = 3,

c + d + f = 3,

c) one or more linear or branched oligosilanes of the general formula (IV)

MepSiqHrCIs (IV),

wherein

q = 3-7

p = q to (2q + 2)

r, s = 0 to (q + 2)

r + s = (2q + 2) - p

and wherein each Si atom bears at least one methyl group,

or mixtures thereof,

2. Process according to embodiment 1 , wherein the starting materials of the general formulae (II), (III) and (IV) do not bear hydrogen substituents, which means that in the disilanes of the general formula (I I) n = 0, in the carbodisilanes of the general formula (I I I) b and d = 0, and in the oligosilanes of the general formula (IV) , r = 0.

3. Process according to embodiments 1 or 2, wherein e + f > 1 .

4. Process according to any of embodiments 1 to 3, wherein s > 1 .

5. Process according to any of embodiments 1 to 4, wherein step A) is carried out by subjecting the methyldisilanes of the general formula (I I), or the carbodisilanes of the general formula (I I I), or the oligosilanes of the general formula (IV), or the mixtures thereof, to the reaction with at least one compound selected from the group consisting of lithium hydride, sodium hydride, potassium hydride, magnesium hydride, calcium hydride, and mixtures thereof.

6. Process according to any of embodiments 1 to 4, wherein step A) is carried out by subjecting the methyldisilanes of the general formula (I I), or the carbodisilanes of the general formula (I I I), or the oligosilanes of the general formula (IV), or the mixtures thereof, to the reaction with at least one compound selected from the group consisting of lithium chloride, sodium chloride, potassium chloride, magnesium chloride, calcium chloride, lithium fluoride, sodium fluoride, potassium fluoride, magnesium fluoride, calcium fluoride, lithium bromide, sodium bromide, potassium bromide, magnesium bromide, calcium bromide and mixtures thereof, and hydrogen chloride.

7. Process according to any of embodiments 1 to 5, wherein step A) is carried out by subjecting the methyldisilanes of the general formula (I I), or the carbodisilanes of the general formula (I I I), or the oligosilanes of the general formula (IV) , or the mixtures thereof to the reaction with at least one compound selected from the group consisting of lithium hydride, and a mixture of lithium chloride and sodium hydride.

8. Process according to any of embodiments 1 to 4, and 6, wherein step A) is carried out by subjecting the methyldisilanes of the general formula (I I), or the carbodisilanes of the general formula (I I I), or the oligosilanes of the general formula (IV), or the mixtures thereof to the reaction with at least one compound selected from the group consisting of lithium chloride, sodium chloride, potassium chloride, and mixtures thereof, and hydrogen chloride.

9. Process according to any of embodiments 1 to 4, wherein step A) is carried out by subjecting the methyldisilanes of the general formula (I I), or the carbodisilanes of the general formula (I I I), or the oligosilanes of the general formula (IV) , or the mixtures thereof to the reaction with at least one compound selected from lithium hydride, sodium hydride, and a mixture of sodium hydride or calcium hydride and lithium chloride, and optionally hydrogen chloride.

10. Process according to any of embodiments 1 to 4, wherein step A) is carried out by subjecting the methyldisilanes of the general formula (I I), or the carbodisilanes of the general formula (I I I), or the oligosilanes of the general formula (IV) , or the mixtures thereof to the reaction with at least one compound selected from lithium chloride and potassium chloride, and hydrogen chloride.

1 1 . Process according to any of the previous embodiments, wherein step A) is carried out in the presence of at least one compound (sometimes referred to as "cleavage compound") selected from the group consisting of

- heterocyclic amines and heterocyclic ammonium halides,

and mixtures of the above-mentioned compounds.

12. Process according to embodiment 1 1 , wherein the quaternary Group 15 onium compound is represented by the formula R₄PCI, wherein R is independently a hydrogen group or an organyl group, more preferably a hydrogen group, an aromatic group or an aliphatic hydrocarbon group.

13. Process according to embodiments 1 1 or 12, wherein the compounds of formula R₄PCI are formed in situ from compounds of formula R₃P and RCI.

14. Process according to any of the previous embodiments 1 1 to 13, wherein the molar ratio of the cleavage compound used in step A) to the silane substrate compounds of the general formulae (I I), (I I I) and (IV) is in the range of about 0.0001 to about 4 mol-%, more preferred about 0.001 to about 0.5 mol-% , even more preferred about 0.01 to about 0.20 mol-%, and most preferably about 0.01 to about 0.1 mol-% based on the molar amount of the silane substrate compounds.

15. Process according to any of the previous embodiments 1 1 to 14, wherein the weight ratio of the cleavage compound used in step A) to the silane substrate is in the range of about 0.01 to about 99.95 wt-% , more preferred about 0.1 to about 55 wt-% , even more preferred about 1 to about 25 wt-% and most preferably about 2 to about 10 wt-% , wherein the weight percentage wt-% is based on the total weight of the silane substrate.

16. Process according to the previous embodiments, wherein step A) is carried out in the presence of at least one compound of the formula R₄PCI.

17. Process according to the previous embodiments, wherein step A) is carried out in the presence of at least one compound of the formula R PCI and at least one methylimidazole.

18. Process according to any of the previous embodiments, wherein step A) is carried out in the presence of n-Bu₄PCI.

19. Process according to any of the previous embodiments, wherein step A) is carried out in the presence of n-Bu PCI and 2-methylimidazole. 20. Process according to the previous embodiments, wherein step A) is carried out in the presence of at least one compound of the formula R₄PCI and at least one metal hydride, preferably lithium hydride (LiH).

21 . Process according to any of the previous embodiments, wherein step A) is carried out in the presence of n-Bu₄PCI and lithium hydride.

22. Process according to the previous embodiments, wherein step A) is carried out in the presence of about 0.5 to about 25 weight-% n-Bu₄PCI wherein the weight percentage wt-% is based on the total weight of the silane substrate and about 25 to about 75 mol-% LiH based on the total molar amount of the chlorine atoms present in silane substrate compounds. 23. Process according to any of the previous embodiments, wherein step A) is carried out using at least one cleavage compound selected from quaternary Group 15 onium compounds represented by the formula R₄QX, wherein each R is independently a hydrogen or an organyl group, Q is phosphorus, arsenic, antimony or bismuth, and X is a halide selected from the group consisting of F, CI, Br and I , at a temperature of about 0 °C to about 300 °C, more preferably about 20 °C to about 220 °C, and even more preferably at about 80 to about 160 °C.

24. Process according to any of the previous embodiments, wherein step A) is carried out using at least one cleavage compound selected from heterocyclic amines and heterocyclic ammonium halides, at a temperature of about 0 °C to about 300 °C, more preferably about 20 °C to about 220 °C, even more preferably at about 100 to about 220 °C, and most preferably at about 140 °C to about 220 °C.

25. Process according to any of the previous embodiments, wherein step A) is carried out using at least one cleavage compound selected from quaternary Group 15 onium compounds represented by the formula R QX, wherein each R is independently a hydrogen or an organyl group, Q is phosphorus, arsenic, antimony or bismuth, and X is a halide selected from the group consisting of F, CI, Br and I, and at least one cleavage compound selected from heterocyclic amines and heterocyclic ammonium halides, at a temperature of about 0 °C to about 300 °C, more preferably about 50 °C to about 220 °C, even more preferably at about 100 to about 200 °C, and most preferably at about 120 °C to about 180 °C.

26. Process according to any of the previous embodiments, wherein step A) is carried out by subjecting the methyldisilanes of the general formula (II), or the carbodisilanes of the general formula (III), or the oligosilanes of the general formula (IV), or the mixtures thereof to the reaction with lithium hydride, or lithium chloride and hydrogen chloride, or a mixture of sodium hydride or calcium hydride and lithium chloride. 27. Process according to any of the previous embodiments wherein before, during or after the cleavage reaction of the substrates of the general formulae (I I), (I I I) and (IV) also a hydrogenation reaction of the substrates or the products of the general formula (I) takes place under the reaction conditions of step A).

28. Process according to any of the previous embodiments, wherein step A) is carried out in the presence of an organic solvent.

29. Process according to any of the previous embodiments, wherein said organic solvent is selected from one or more ether compounds.

30. Process according to any of the previous embodiments, wherein said organic solvent is a mixture of one or more ether compounds and one or more non-ether compounds.

31 . Process according to any of the previous embodiments, wherein said ether compounds are selected from the group of linear, cyclic or complexing ether compounds.

32. Process according to any of the previous embodiments, wherein the ether compound is selected from the group consisting of linear ethers, such as diethyl ether, di-n-butyl ether, complexing ethers, such as dimethoxy ethane, diethylene glycol dimethyl ether (diglyme) , tetraethylene glycoldimethyl ether (tetraglyme), alkylated polyethylene glycols (alkylated PEGs), cyclic ethers such as dioxane, preferably 1 ,4-dioxane, 2-methyltetrahydrofuran, tet ra hyd rof u ra n , t etra hyd ro py ra n .

33. Process according to any of the previous embodiments, wherein the ether compound is a high-boiling ether compound, most preferably diglyme or tetraglyme.

34. Process according to any of the previous embodiments, wherein step A) is conducted at a temperature of about 0 °C to about 220 °C, preferably about 20 °C to about 180 °C, more preferably about 20 °C to about 140 °C, most preferably about 60 °C to about 140 °C.

35. Process according to any of the previous embodiments, wherein step A) is conducted at a pressure of about 0.1 bar to about 30 bar, preferably about 1 bar to about 20 bar, most preferably about 1 bar to about 10 bar.

36. Process according to any of the previous embodiments, wherein in the step A) the weight ratio of the methyldisilanes of the general formula (I I) , the carbodisilanes (I I I) or the oligosilanes of the general formula (IV) , or mixtures thereof to the organic solvent is less than about 4: 1 , preferably in the range of about 2: 1 to about 1 : 1 , more preferably about 1 :2 to about 1 :20.

37. Process according to any of the previous embodiments, wherein the molar ratio of hydride anions stemming from the at least one compound selected from the group consisting of an alkali metal hydride or alkaline earth metal hydride or mixtures thereof, to the chlorine atoms present in the methyldisilanes of the general formula (I I) , the carbodisilanes (I II), or the oligosilanes of the general formula (IV) , or mixtures thereof is in the range of about 1 to about 600 mol-%, more preferred about 25 to about 400 mol-%, even more preferred about 25 to about 200 mol-%, and most preferred about 25 to about 100 mol-%.

38. Process according to any of the previous embodiments, wherein the molar ratio of halide anions stemming from the at least one compound selected from the group consisting of an alkali metal halide or alkaline earth metal halide or mixtures thereof, to the methyldisilanes of the general formula (II) , the carbodisilanes (I I I) or the oligosilanes of the general formula (IV), or mixtures thereof is in the range of about 1 to about 600 mol-%, more preferred about 25 to about 400 mol-%, even more preferred about 25 to about 200 mol-% , and most preferred about 25 to about 100 mol-%.

39. Process according to any of the previous embodiments, wherein the molar ratio of lithium chloride to the methyldisilanes of the general formula (I I) , the carbodisilanes (I I I), or the oligosilanes of the general formula (IV) or mixtures thereof is in the range of about 1 to about 600 mol-%, more preferred about 25 to about 400 mol-%, even more preferred about 25 to about 100 mol-%, and most preferred about 25 to about 50 mol-% .

40. Process according to any of the previous embodiments, wherein the molar concentration of the at least one compound selected from the group consisting of an alkali metal halide, an alkaline earth metal halide, an alkali metal hydride or alkaline earth metal hydride or mixtures thereof, used for cleavage is in the range of about 0.0001 to about 15 mol/l, more preferred about 0.05 to about 10 mol/l, even more preferred about 0.5 to about 5 mol/l, and most preferred about 0.5 to about 3 mol/l based on the volume of the reaction mixture in step A) .

41 . Process according to any of the previous embodiments, wherein step A) is conducted in the presence of HCI.

42. Process according to any of the previous embodiments, wherein step A) is conducted in the presence of HCI and LiCI or HCI and KCI.

43. Process according to previous embodiments 41 or 42, wherein the molar ratio of the methyldisilanes of the general formula (I I), or the carbodisilanes of the general formula (I I I) , or the oligosilanes of the general formula (IV) , or the mixtures thereof to HCI is about 0.2 to about 5, more preferably about 0.5 to about 2, even more preferably about 0.75 to about 1 .25, and most preferably about 1 : 1 .

44. Process according to any of the previous embodiments, wherein step A) is carried out in diglyme or tetraglyme as solvent.

45. Process according to any of the previous embodiments, wherein the methyldisilanes of the general formula (I I), or the carbodisilanes of the general formula (I II), or the oligosilanes of the general formula (IV) , or the mixtures thereof are residues of the Rochow-Muller Direct Process (DPR) . 46. Process according to any of the previous embodiments, wherein the methylmonosilanes of the general formula (I) are selected from the group consisting of MeSiC , Me₂SiHCI, MeSiH₂CI, MeSiHCb, Me₃SiCI, Me₃SiH, MeSihh, Me₂SiCI₂ and Me₂SiH₂.

47. Process according to any of the previous embodiments, wherein the methylmonosilanes of the formula (I) are selected from the group consisting of Me₂SiHCI,

MeSiH₂CI and MeSiHCb.

48. Process according to any of the previous embodiments, wherein dimethylchloromonosilane Me₂SiHCI is formed by submitting a substrate comprising one or more silanes selected from the group consisting of CIMe₂Si-SiMe₂CI, CIMe₂Si-SiMeCI₂, Me₃Si-SiMe₂CI, HMe₂Si-SiMe₂H, HMe₂Si-SiMeH₂, Me₃Si-SiMe₂H, CIMe₂Si-SiMe₂H, CIMe₂Si- SiMeH₂, HMe₂Si-SiMeCI_2, CIMe₂Si-CH₂-SiMeCI₂, CIMe₂Si-CH₂-SiMe₂CI, Me₃Si-CH₂-SiMe₂CI, CIMe₂Si-SiMe₂-SiMe₂CI, CIMe₂Si-SiMe₂-SiMe₂-SiMe₂CI and (CIMe₂Si)₃SiMe to the cleavage reactions of step A).

49. Process according to any of the previous embodiments, wherein methylchloromonosilane MeSiH₂CI is formed by submitting a substrate comprising one or more silanes selected from the group consisting of CI₂MeSi-SiMeCI₂, CI₂MeSi-SiMe₂CI, CI₂MeSi-SiMe₃, H₂MeSi-SiMeH₂, H₂MeSi-SiMe₂H, H₂MeSi-SiMe₃, HCIMeSi-SiMeH₂, HCIMeSi-SiMeCIH, HCIMeSi-SiMeCb, CI₂MeSi-SiMeH₂, CIHMeSi-SiMe₂CI, CI₂MeSi-SiMe₂H, CIHMeSi-SiMe₂H, H₂MeSi-SiMe₂CI, CI₂MeSi-CH₂-SiMeCI₂, CIMe₂Si-CH₂-SiMeCI₂, Me₃Si- CH₂-SiMeCI₂, (CI₂MeSi)₂SiMeCI, (CI₂MeSi)₃SiMe, (CI₂MeSi)₂SiMe-SiCIMe-SiCI₂Me, [(CI₂MeSi)₂SiMe]₂, [(CI₂MeSi)₂SiMe]₂SiCIMe and (CI₂MeSi)₂SiMe-SiMe₂CI to the cleavage reactions of step A).

50. Process according to any of the previous embodiments, wherein

methyldichloromonosilane MeSiHCb is formed by submitting a substrate comprising one or more silanes selected from the group consisting of CI₂MeSi-SiMeCI₂, CI₂MeSi-SiMe₂CI,

CI₂MeSi-SiMe₃, HCIMeSi-SiMeH₂, HCIMeSi-SiMeCIH, HCIMeSi-SiMeCb, CI₂MeSi-SiMeH₂, CIHMeSi-SiMe₂CI, CI₂MeSi-SiMe₂H, CIHMeSi-SiMe₂H, H₂MeSi-SiMe₂CI, CI₂MeSi-CH₂- SiMeCb, CIMe₂Si-CH₂-SiMeCI₂, Me₃Si-CH₂-SiMeCI₂, (CI₂MeSi)₂SiMeCI, (CI₂MeSi)₃SiMe, (CI₂MeSi)₂SiMe-SiCIMe-SiCI₂Me, [(CI₂MeSi)₂SiMe]₂, [(CI₂MeSi)₂SiMe]₂SiCIMe and

(CI₂MeSi)₂SiMe-SiMe₂CI to the cleavage reactions of step A).

51 . Process according to any of the previous embodiments, wherein the step B) of separating the resulting methylmonosilanes of the formula (I) is carried out by condensation, distillation or a combination thereof.

52. Process according to any of the previous embodiments, wherein the step B) of separating the resulting methylmonosilanes of the formula (I) is carried out by distillation. 53. Process according to any of the previous embodiments, wherein the process is carried out under inert conditions.

54. Methylmonosilanes of the general formula (I) as defined above, as obtainable by the process according to any of the previous embodiments.

55. Compositions comprising at least one methylmonosilane of the general formula (I) as defined above, as obtainable by the process according to any of the previous embodiments.

EXAMPLES

The present invention is further illustrated by the following examples, without being limited thereto. General

Mixtures of methyldisilanes, carbodisilanes and methyloligosilanes formed as residue in the Direct Process of formation of methylchlorosilanes were reacted with alkali- and alkaline earth metal chlorides, preferably however with lithium hydride in complex ethers such as diglyme or tetraglyme. Prior before reaction the metal salts as well as the solvents used were carefully dried according to procedures known from literature. The reactions investigated were generally performed in sealed NMR tubes first to prevent evaporation of low boiling reaction products, such as hydrogenated organomonosilanes, and to elucidate the reaction conditions (temperature, time) for silicon-silicon bond cleavage. Subsequently, these conditions were exemplarily transferred onto cleavage reactions in a preparative scale in an open system, preferably a multi-necked flask, equipped with a magnetic stirrer, thermometer, dropping funnel, and a reflux condenser that was connected with a cooling trap to collect low boiling reaction products. Products formed were isolated by combined condensation/distillation procedures. Products were analyzed and characterized by standard procedures, especially by NMR spectroscopy and GC/MS analyses.

Identification of products

Products were analyzed by ¹ H, ²⁹Si and ¹ H-²⁹Si-HSQC NMR spectroscopy. The spectra were recorded on a Bruker AV-500 spectrometer equipped with a Prodigy BBO 500 S1 probe. ¹ H- NMR spectra were calibrated to the residual solvent proton resonance ([D₆]benzene <5_H = 7.16 ppm). Product identification was additionally supported by GC-MS analyses and verified identification of the main products. GC-MS analyses were measured with a Thermo Scientific Trace GC Ultra coupled with an ITQ 900MS mass spectrometer. The stationary phase (Machery-Nagel PERMABOND Silane) had a length of 50 m with an inner diameter of 0.32 mm. 1 μΙ of analyte solution was injected, 1/25 thereof was transferred onto the column with a flow rate of 1 .7 mL/min carried by Helium gas. The temperature of the column was first kept at 50 °C for 10 minutes. Temperature was then elevated at a rate of 20 °C/min up to 250 °C and held at that temperature for another 40 minutes. After exiting the column, substances were ionized with 70 eV and cationic fragments were measured within a range of 34 - 600 m/z (mass per charge). Product mixtures were diluted with benzene prior to the measurement.

The characteristic ²⁹Si-NMR chemical shifts and coupling constants ¹J{²⁹Si-¹H} for the starting materials reacted with the alkali- and alkaline earth metal salts and the products formed, are listed in Table 1.

Table 1 : Identification of starting materials and products

Example 1 :

A mixture of 1 12 mg highly chlorinated disilanes 1 (69 mol%), 2 (26 mol%), 3 (4 mol%) and 4 (1 mol%) were reacted with 8.1 mg LiH (50 mol%, in relation to chlorine content in the mixture) in diglyme as solvent. Cleavage and reduction of chloro-mono- and disilanes started at r.t. as indicated by warming up of the reaction mixture. The products formed are listed in Table 2. The cleavage of disilanes was nearly quantitative, only highly methylated disilane 3 remained in traces (~1%). Monosilane 9 is the main product followed by monosilane 8. Table 2

Example 2:

Cleavage reaction of the methylchlorodisilane mixture (183 mg) of the sample from Example 1 with LiH in diglyme can easily be controlled by the amount of LiH reacted. Reduction of LiH to 41 mol% (10 mg (when compared to Example 1) avoids formation of the low boiling monosilane 10, instead dichlorsilanes 8 and 11 became the main products. The overall product composition is listed in Table 3, about 2% disilanes remained unreacted. The reaction occurred at r.t. under self-heating of the sample to about 40 °C.

Table 3

Example 3:

The results of Example 2 are further supported by the results of treating the mixture of disilanes (1 10 mg - 159 mg) of Example 1 with different molar amounts of LiH (25, 50, 75, 100 and 400 mol-%) in diglyme. All reactions occurred at r.t. with self-heating of the samples. The products formed are listed in Table 4 and demonstrate convincingly that after cleavage of the silicon-silicon bonds the resulting chlorinated monosilanes are further transformed into hydrogen-substituted monosilanes by LiH. The higher the chloro substitution at Si is, the faster hydrogenation occurs: MeSiC > Me₂SiCI₂ > Me₃SiCI. The same is true for the only partially hydrogenated monosilanes MeH₂SiCI > MeSiHC > Me₂SiHCI. Especially the latter reacts very slowly because the molar amount of this chlorosilane remains nearly constant in all reactions performed. With high excess of LiH (about 400 mol%) all chloro substituted monosilanes are completely reacted to the per hydrogenated silanes 13 (6%) 10 (78%) and the per hydrogenated disilanes 16, 17, 18 and 19. The results of this series of experiments are listed in the Table 4. In summary, for the preferred synthesis of monohydrogenated silanes such as 8 and 12, LiH should be used in stoichiometric deficit (< about 25 mol%), for an increase of the amount of monosilane 9 the molar amount of LiH is best about 25 to about 75 mol%. For a complete formation of perhydrido-methylsilanes (10 and 13) LiH should be used in excess.

Table 4

*: This experiment was performed to prove reproducibility of Example 1

Example 4:

A mixture (96 mg) of the highly methylated disilanes 3 (61 mol%) and 5 (30 mol%) with traces of 2 (5 mol%) and 4 (4 mol%) was reacted with different molar ratios of LiH in diglyme at different reaction temperatures. While highly chlorinated disilanes started to react already at r.t. with self-heating, highly methylated disilanes did not react under comparable conditions. Instead, chlorodisilane hydrogenation slowly started at r.t. and is accelerated with increasing temperature and the amount of LiH reacted. Disilane cleavage slowly started at 140 °C with 77 mol% LiH and monosilanes 13 and 15 were formed in small amounts. Even with an small excess of LiH (1 10 mol%) monosilane formation is only 8 mol%, with 350 mol% LiH the chlorinated disilanes were completely transformed into their hydrogen substituted congeners at r.t.. At 140 °C Me₂SiH₂ was formed in 42%, Me₃SiH was 3%. As can be seen from Table 5, the disilanes Me₃Si-SiMe₂H and HMe₂Si-SiMe₂H were slowly cleaved into monomers, the latter faster than pentamethyldisilane. Table 5

Example 5:

The reaction of a complex mixture (131 - 238 mg) of mainly highly chlorinated disilanes and monosilanes as displayed in Table 6 was reacted with 41 mol% or 73 mol% LiH, respectively, in diglyme at r.t. with self-heating. The products formed are listed in Table 7 and show that monosilanes are formed in 96%, 4% of tetramethyldichloro- and pentamethylchlorodisilane remained unreacted. Higher amounts of LiH lead to increasing amounts of hydrogen substituted silanes by Si-CI- Si-H reduction.

Table 6

Example 6:

A complex mixture (149 - 171 mg) mainly consisting of mono- and highly methylated disilanes as displayed in Table 8 was reacted with 51 mol% and 100 mol% of LiH, respectively, in diglyme at r.t. with self-heating. The products formed are listed in Table 9 and show that 62% and 68% monomers, respectively, were formed.

The higher amount of LiH increased monomer formation as well as conversion of disilanes 3 and 5. The relatively high yields of monosilane 10 result from hydrogenation of the corresponding chlorosilane already present in the starting mixture of compounds. Again, disilane cleavage is faster with higher degree of chlorination at the disilane moiety. Noteably, even the carbodisilanes within the starting mixture were cleaved to give monosilanes besides traces of oligomeric material.

Table 8

Example 7:

A complex mixture (149 - 166 mg) of chlorinated monosilanes, disilanes and carbodisilanes as displayed in Table 10 was reacted with LiH (50 and 100 mol%, respectively) in diglyme at r.t. and at 140 °C (100 mol% LiH). The products formed are listed in Table 1 1 and demonstrate that at 140 °C even the highly chlorinated carbodisilanes (C MeSi)2CH2 and CIMe2Si-CH2-SiMeCl2 were cleaved mostly giving monosilane 10. Only 2% of pentamethyldisilane remained uncleaved.

Table 10

Table 11

Example 8:

A mixture of highly chlorinated disilanes (122 mg) of the same composition as in Example 1 was reacted with 50 mol% of sodium hydride (NaH) in diglyme. At r.t. and 60 °C (1 h) no reaction was detected. Warming the sample to 140 °C (30 h) initiated the cleaving reaction to yield monosilanes in 74%. The product composition is given in Table 12. 46.6 mol% of the disilanes remained unreacted.

Table 12

Example 9:

The mixture of Example 1 (244 mg) was reacted with 50 mol% of CaH₂ in diglyme. Reaction started at 140 °C (30 h). About 92% of monosilanes were formed, 8% of disilanes remained unreacted. The product composition is listed in Table 13.

Table 13

Example 10 (Comparative):

A mixture of partially and perhydrogenated disilanes (200 mg) as displayed in Table 14 was reacted with lithium chloride (LiCI) in diglyme as solvent. Cleavage reactions started at 60 °C (3 h) to give 48% of monosilanes. This yield was increased to 69% at 140 °C (6 h), as can be seen in Table 15. Methyldisilanes were cleaved faster compared to those derivatives that are only partly hydrogenated. Notably, obviously chlorination reactions occur, because monochlorinated disilane 21 was formed from its reduced precursor already at 60 °C (3 h). In contrast to H-substituted disilanes, the methylchloro-derivatives were not cleaved by LiCI at this temperature.

Table 14

The amount of the preferred silanes MeSihbCI and MeSiHC was comparatively low.

Examples of hydrogenation and cleavage reactions in open systems

Hydrogenation and cleavage reactions of complex mixtures of mono- and disilanes with different molar amounts of LiH in diglyme in an open system: In a 500 mL three-necked flask, equipped with a reflux condenser, a dropping funnel, thermometer and magnetic stirrer, 820 mg (103 mmol, 44 mol%) of LiH were suspended in 20 mL diglyme under inert nitrogen atmosphere. A cooled trap (-196 °C) was connected with the top of the reflux condenser to collect low boiling monosilanes that evaporate from the reaction mixture under normal pressure.

Example 11

14.98 g of a mixture comprising of mono- and disilanes as displayed in Table 16 were added to the LiH/diglyme suspension and slowly heated to 100-130 °C over a period of 5.5 h. The reaction products formed were evaporated and collected in the cold trap and condensed into an ampoule (- 196 °C) under vacuo upon warming to r.t.. The silane mixture obtained is listed in Table 17 and demonstrates that methylchlorosilanes 8 (36.1 %), 9 (15.2%) and methylsilanes 10 (15.2%) were formed as major products besides 11 (16.5%).

The residue, still dissolved in diglyme, consisted of monosilanes and highly methylated disilanes 3 and 5 that can ^'t be cleaved by LiH under moderate conditions. The molar ratio of products remaining in diglyme is given in Table 18.

Table 16- 18 convincingly prove Si-Si bond cleavage of methylchlorodisilanes having more than one chlorine substituents at the silicon backbone with subsequent reduction of chlorinated monosilanes to yield hydridosilanes under moderate conditions.

Table 16

Table 17

Table 18

Compound mol%

Me₂SiCI₂ 56.7

MesSiCI 2.8

MeSiCIs 9.1

Me₂SiHCI 5.7

MeSiHCI₂ 13.6

Me₃Si-SiMe₂CI 4.5

CIMe₂Si-SiMe₂CI 7.5 Example 12

In analogy to Example 11 , 10.62 g of a mixture of mono- and disilanes as displayed in Table 19 was reacted with 0.92 g (0.1 12 mol, 84 mol%) LiH in 6 mL diglyme to give the products listed in Table 20 that were collected in the -196 °C cooling trap and subsequently condensed in an ampoule in vacuo. The reaction time was 5 h, the reaction temperature was 130 °C.

As can be seen from Table 20, MeSiH₃ 10 is the main product (~34%) followed by 7 with nearly 12% and Me2SiH2 13 in about 10%. Related to the relatively high amount of LiH, cleavage of highly chlorinated disilanes and hydrogenation to give methylhydridodisilanes obviously occurred simultaneously. About 7.5% of perhydrogenated methyldisilanes remained uncleaved, besides permethylated disilane 6 (2.8%) and dichlorinated disilane 3 (in traces, 1.1%). The reaction residue mainly contained disilanes as well as carbodisilanes, as shown in Table 21.

Table 19

Table 20

Table 21

Example 13

10.1 1 g of a complex mixture comprising mono- and disilanes as well as carbodisilanes as shown in Table 22 was reacted with 1.1 1 g (0.135 mol, 92 mol%) of LiH in 7 mL diglyme for 5 h at 130 °C. The volatile products formed and separated by condensation are listed in Table 23. According to the high amount of LiH, monosilanes 10 (41 %) and 13 (30%) were main cleavage/hydrogenation products. Highly methylated hydrogen substituted disilanes and carbodisilanes were formed but remained mostly uncleaved. In the reaction residue highly methylated disilanes and carbodisilanes were detected, as displayed in Table 24. Table 22

Table 23

Table 24

Example 14

1 10.9 g of a mixture containing mono- and disilanes which reflects an industrial DPR (see Table 25) were reacted with 9.15 g (1 .15 mol, 43 mol%) of LiH in 60 mL diglyme at 130 °C for 5 h. The obtained volatile products that evaporated into the -196 °C cooling trap are listed in Table 26 and prove Me₂SiCI₂ (11 , 36%), MeSiC (7, 18.5%) and MeSiHC (8, 16%) to be main products with nearly 71 %. For increasing of yields of the technically most valuable monosilanes, and simplification of work up, the low boiling monosilanes 9 and 10 were directly evaporated into a HCI/diglyme solution to finally give Me₂SiHCI (12, 36.2%), MeSihbCI (9, 49.4%) and MeSiHC (8, 7.2%) in nearly 93%, as displayed in Table 27. The reaction residue only contained the disilanes 3 (32.7%) and 5 (56.3%) besides carbodisilanes (1 1 %), as can be seen from Table 28.

Table 25

Table 26

Table 27

Table 28

Example 15

14.72 g of a mixture comprising of mono- and disilanes as displayed in Table 16 of Example 1 1 were added to 4.03 g NaH (101 mmol, 60% in mineral oil, 43.3 mol% in relation to the chlorine content of the starting mixture) and 1.57 g LiCI (37 mmol) suspended in 7.5 mL diglyme. The reaction started immediately with self-heating of the mixture to 50 °C. After complete addition, the reaction mixture was heated to 150 °C for 5.5 h. Upon warming, the reaction products formed were evaporated and collected in the cold trap and condensed into an ampoule (-196 °C) under vacuo. The silane mixture obtained is listed in Table 29 and demonstrates that the highly chlorinated disilanes 1 , 2 and also 4 already were cleaved with a mixture of NaH/LiCI to give mostly chlorosilanes 11 and 7, but also hydrogenated monosilanes (6%). In this reaction, LiCI act as catalyst to generate in situ LiH with NaH that hydrogenated mono- and disilanes.

Table 29

Example 16

14.72 g of a mixture comprising of mono- and disilanes as displayed in Table 19 of Example 12 were added to 8.30 g NaH (208 mmol, 60% in mineral oil, 77.5 mol% in relation to the chlorine content of the starting mixture) and 2.07 g LiCI (49 mmol) suspended in 10 mL diglyme. The reaction starts immediately with self-heating to 50 °C. After complete addition, the reaction mixture was heated to 150 °C for 5.5 h. Upon warming the reaction products formed were evaporated and collected in the cold trap and condensed into an ampoule (-196 °C) under vacuo. The products of the mixture obtained are listed in Table 30, which clearly shows that hydrogenated monosilanes were formed (~16%) using a mixture of a low- cost hydrogen source (NaH) and an alkali metal salt (LiCI). The reaction residue contained carbodisilanes, highly methylated disilanes and traces of monosilanes MeSiC and Me₂SiCI₂, besides some oligosilanes which formed during disproportionation.

Table 30

Example 17

Performing the disilane cleavage accompanied by Si-CI- Si-H reduction with lithium hydride or a mixture of NaH/LiCI to prepare LiH in situ, lithium chloride formed as by-product. Based on its solubility in complexing ethers (e.g. diglyme and tetraglyme) it was found that the lithium chloride solely was able to cleave silicon-silicon bonds upon warming a fraction of highly chlorinated disilanes (composition of the starting mixture is listed in Table 16) in the respective ether (see Table 31). In order to check the general ability of alkali- and/or alkaline earth chlorides or dichlorides for disilane cleavage, metal chlorides, some in a mixture with NaH as Si-CI reduction agent (as LiH equivalent), were mixed in an NMR tube, frozen (- 196 °C) evacuated and sealed in vacuo. NMR spectra were taken reacting the samples with increasing reaction temperatures and reaction times. The results of the experiments performed are listed in Table 31 and prove the general ability of alkali/alkaline earth metal salts for Si-Si bond cleavage, the addition of NaH or CaH₂ supported formation of reduced monosilanes. Transferring metal salt splitting of disilanes into a preparative scale (see Examples 18 and 19) it became obvious that upon reaction an oligomeric mixture of polysilanes was formed. According to investigations of the Roewer group (J. Organometal. Chem., 507 (1996), 221-228) formal trisilane formation thus demonstrates that two molecules of disilanes are giving a trisilane and only one molecule of monosilane. This reaction pathway might be true for LiH cleavage too. Moreover, the formation silyl lithium species by disilane splitting seems to be possible (J. Organometal. Chem. 9 (1967) 421-426; Inorganic Chemistry Vol. 6 No. 7 (1967) 1429-1431). Notably, even tri- and higher oligosilanes were split with the salts investigated, thus the molar ratios of monosilanes formed differs from the theoretical mass balance calculated for defined systems. Products [mol%]

Example 18 (Comparative)

1 1 .91 g of a mixture comprising of mono- and disilanes as displayed in Table 16 were added to 2.88 g LiCI (68 mmol) suspended in 10 mL of diglyme. The reaction mixture was heated to 145 °C for 5.5 h. Upon warming to r.t. the reaction products formed were evaporated and collected in the cold trap and condensed into an ampoule (-196 °C) under vacuo upon warming to r.t.. The silane mixture obtained is listed in Table 32 and demonstrates that the cleavage of highly chlorinated disilanes can be carried out in preparative scale to give methylchlorosilanes 7 and 11 in high yields. In the residue remaining carbosilanes, highly methylated disilanes and traces of monosilanes MeSiC and Me₂SiCI₂ were detected besides oligosilanes, which formed during disproportionation.

Table 32

As can be seen from table 32 no hydridosilanes are formed. Example 19 (Comparative)

59.6 g of a mixture comprising of mono- and disilanes as displayed in Table 16 were added to 1 .98 g KCI (26 mmol) suspended in 10 mL of diglyme. The reaction mixture was heated to 145 -170 °C for 18 h. The reaction products formed were distilled off and their molar ratio is listed in Table 33. The product composition demonstrates that the cleavage of highly chlorinated disilanes is carried out in preparative scale to give methylchlorosilanes 7 and 11. MeSiHC (8, ~1 %) formation might be explained due to carbodisilane formation (Organometallics, 2, (1983), 859-864). Notably, potassium chloride was used in this disilane cleavage reaction as catalyst (3.3 weight%). In the reaction residue carbosilanes, highly methylated disilanes and traces of monosilanes MeSiC and Me₂SiCI₂ could be identified besides larger amounts of oligosilanes that were remaining in the residue, which were formed upon disproportionation. Table 33

As can be seen from table 33 the amount of the formed hydridosilane MeSiHC is very low.

Example 20

A mixture of mono- and disilanes (238 mg, listed in Table 34) was reacted with lithium chloride (101 mg) in a diglyme/HCI solution (molar ratio Disilane/HCI 1 : 1) at 80°C (71 h) to give monomers nearly quantitatively (listed in Table 35). For this reaction no other hydrogen sources were used instead of HCI. HCI reacted as a silylene trapping agent, the silylene cannot insert into the Si-Si-bond to build up oligomeric structures. The main products after reaction were MeSiCb (34.0%) and MeSiHCb (30.5%).

Table 34

Compared to example 19, the amount of MeSiHCb is considerably increased. Example 21

A mixture of mono- and disilanes (238 mg, listed in Table 36) was reacted with potassium chloride (95 mg) in a tetraglyme/diglyme/HCI solution (molar ratio Disilane/HCI 1 :1) at 80°C (71 h) to give monomers in 51.4% (listed in Table 37). Trichlorotrimethyldisilane (2) was cleaved before tetrachlorodimethyldisilane (1) to give Me₂SiCI₂ (11 , 37.8%) and MeSiHC (8, 9.8%). Increasing the temperature to 100 °C (23.5 h) gave monomers in 69.5% and unreacted disilanes listed in Table 37. No oligomeric structures were observed. For this reaction no other hydrogen sources were used except HCI. HCI reacted as a silylene trapping agent, the silylene cannot insert into the Si-Si-bond to build up oligomeric structures. The main products after reaction were Me₂SiCI₂ (42.6%) and MeSiHCb (19.2%).

Table 36

Table 37

Example 22

Disilane 1 was reacted with 33, 66, 100 and 200 mol% LiH (in relation to the chlorine content) in diglyme as solvent in a sealed NMR tube. Cleavage and reduction of chloro-mono- and disilanes started already at r.t. as indicated by warming of the reaction mixture up to 60 °C. Further heating of the sample to 60 °C for 7.5 h increased hydrogenation of the monosilanes MeSiCb to MeSiH3 and of MeSiHCb to give MeSiH₂CI. Oligomeric structures were only detected in case higher concentrations of LiH (200 mol%) were used, but completely disappeared after heating the sample to 60 °C. At 100°C the product composition in all cases is strongly dominated by hydridomonosilanes (33mol% LiH: 98%; >66mol% LiH: 100%; 200mol% LiH gives pure MeSiH₃ quantitatively). The results obtained for this series of experiments are listed in Tables 38 to 41.

Table 38

Table 39

Table 40

Table 41

Example 23

Disilane 1 was reacted with 33 mol% LiH (in relation to the chlorine content) in THF as solvent in a sealed NMR tube. Cleavage and reduction of chloro-mono- and disilanes started already at r.t. as indicated by warming of the reaction mixture up to 60 °C. Additional heating of the sample to 60 °C for 7.5 h accelerated hydrogenation of monosilanes formed upon disilane cleavage, similarly as described for Example 22. At 100°C hydridomonosilane formation is more than 96%. Product distribution from the reaction starting at r.t. and increasing temperature to 100 °C is listed in Table 42. No oligomeric compounds were detected in the corresponding ²⁹Si-NMR spectra of the reaction mixtures.

Table 42

Example 24 (Comparative)

Disilane 1 (254mg) was reacted with LiCI (212 mg) in THF as solvent in a sealed NMR tube. Cleavage reaction started already at r.t. to give MeSiCI₃. Further heating of the sample to 60 °C for 7.5 h forced disilane cleavage, 1 remained in 58 % in the reaction mixture besides 2.3 % of oligosilanes. Formation of MeSiC was further increased to about 55mol% at 100°C. Products formed between r.t. and 100 °C are listed in Table 43.

Table 43

No hydridosilanes are formed, and cleavage performance was poor.

Claims

1. Process for the manufacture of methylmonosilanes of the general formula (I): MexSiHyClz (I), wherein

x = 1 to 3,

y = 0 to 3, preferably 1 to 3,

z = 0 to 3 and

x + y + z = 4,

comprising:

A) the step of subjecting a silane substrate comprising one or more silanes selected from the group of a) one or more methyldisilanes of the general formula (II)

Me_mSi₂H_nClo (II)

wherein

m = 1 to 6,

n = 0 to 5

o = 1 to 5 and

m + n + o = 6,

b) one or more carbodisilanes of the general formula (III)

(MeaSiH_bCle)-CH2-(Me_cSiH_dCl_f) (III)

wherein

a, c are independently of each other 1 to 3,

b, d are independently from each other 0 to 2 e, f are independently from each other 0 to 2,

a + b + e = 3,

c + d + f = 3,

c) one or more linear or branched oligosilanes of the general formula (IV)

MepSiqHrCIs (IV),

wherein

q = 3-7

p = q to (2q + 2)

r, s = 0 to (q + 2)

r + s = (2q + 2) - p

and wherein each Si atom bears at least one methyl group,

or mixtures thereof,

2. Process according to claim 1 , wherein the starting materials of the general formulae (II), (III) and (IV) do not bear hydrogen substituents, which means that in the disilanes of the general formula (II) n = 0, in the carbodisilanes of the general formula (III) b and d = 0, and in the oligosilanes of the general formula (IV), r = 0.

3. Process according to claims 1 or 2, wherein e + f > 1 and s > 1 .

4. Process according to any of claims 1 to 3, wherein step A) is carried out by subjecting the methyldisilanes of the general formula (II), or the carbodisilanes of the general formula (II I), or the oligosilanes of the general formula (IV), or the mixtures thereof, to the reaction with at least one compound selected from the group consisting of lithium hydride, sodium hydride, potassium hydride, magnesium hydride, calcium hydride, and mixtures thereof, preferably to the reaction with at least one compound selected from the group consisting of lithium hydride, and a mixture of lithium chloride and sodium hydride, and mixtures thereof.

5. Process according to any of claims 1 to 3, wherein step A) is carried out by subjecting the methyldisilanes of the general formula (II), or the carbodisilanes of the general formula

(II I), or the oligosilanes of the general formula (IV), or the mixtures thereof, to the reaction with at least one compound selected from the group consisting of lithium chloride, sodium chloride, potassium chloride, magnesium chloride, calcium chloride, lithium fluoride, sodium fluoride, potassium fluoride, magnesium fluoride, calcium fluoride, lithium bromide, sodium bromide, potassium bromide, magnesium bromide, calcium bromide and mixtures thereof, and hydrogen chloride, preferably to the reaction with at least one compound selected from the group consisting of lithium chloride, sodium chloride, potassium chloride, and mixtures thereof, and hydrogen chloride.

6. Process according to any of claims 1 to 3, wherein step A) is carried out by subjecting the methyldisilanes of the general formula (II), or the carbodisilanes of the general formula

(II I), or the oligosilanes of the general formula (IV), or the mixtures thereof to the reaction with at least one compound selected from lithium hydride, sodium hydride, and a mixture of sodium hydride or calcium hydride and lithium chloride, and optionally hydrogen chloride, or wherein step A) is carried out by subjecting the methyldisilanes of the general formula (II), or the carbodisilanes of the general formula (III), or the oligosilanes of the general formula (IV), or the mixtures thereof to the reaction with at least one compound selected from lithium chloride and potassium chloride, and hydrogen chloride.

7. Process according to any of the previous claims, wherein step A) is carried out in the presence of at least one compound (sometimes referred to as "cleavage compound") selected from the group consisting of

- a quaternary Group 15 onium compound R4QX, wherein each R is independently a hydrogen or an organyl group, Q is phosphorus, arsenic, antimony or bismuth, and X is a halide selected from the group consisting of F, CI, Br and I,

- heterocyclic amines and heterocyclic ammonium halides,

and mixtures of the above-mentioned compounds.

8. Process according to any of the previous claims wherein before, during or after the cleavage reaction of the substrates of the general formulae (II), (III) and (IV) also a hydrogenation reaction of the substrates or the products of the general formula (I) takes place under the reaction conditions of step A).

9. Process according to any of the previous claims, wherein step A) is carried out in the presence of an organic solvent, preferably said organic solvent is selected from one or more ether compounds.

10. Process according to any of the previous claims, wherein step A) is conducted in the presence of HCI.

1 1 . Process according to any of the previous claims, wherein step A) is conducted in the presence of HCI and LiCI or HCI and KCI.

12. Process according to previous claims 10 or 1 1 , wherein the molar ratio of the methyldisilanes of the general formula (II), or the carbodisilanes of the general formula (III), or the oligosilanes of the general formula (IV), or the mixtures thereof to HCI is about 0.2 to about 5, more preferably about 0.5 to about 2, even more preferably about 0.75 to about 1 .25, and most preferably about 1 : 1 .

13. Process according to any of the previous claims, wherein the methyldisilanes of the general formula (II), or the carbodisilanes of the general formula (III), or the oligosilanes of the general formula (IV), or the mixtures thereof are residues of the Rochow-Muller Direct Process (DPR).

14. Process according to any of the previous claims, wherein the methylmonosilanes of the general formula (I) are selected from the group consisting of MeSiCI₃, Me₂SiHCI, MeSiH₂CI, MeSiHCb, Me₃SiCI, Me₃SiH, MeSiH₃, Me₂SiCI₂ and Me₂SiH₂, preferably the methylmonosilanes of the formula (I) are selected from the group consisting of Me₂SiHCI, MeSiH₂CI and MeSiHCb.

15. Process according to any of the previous claims, wherein

dimethylchloromonosilane Me₂SiHCI is formed by submitting a substrate comprising one or more silanes selected from the group consisting of CIMe₂Si-SiMe₂CI, CIMe₂Si-SiMeCI₂, Me₃Si-SiMe₂CI, HMe₂Si-SiMe₂H, HMe₂Si-SiMeH₂, Me₃Si-SiMe₂H, CIMe₂Si-SiMe₂H, CIMe₂Si- SiMeH₂, HMe₂Si-SiMeCI_2, CIMe₂Si-CH₂-SiMeCI₂, CIMe₂Si-CH₂-SiMe₂CI, Me₃Si-CH₂-SiMe₂CI, CIMe₂Si-SiMe₂-SiMe₂CI, CIMe₂Si-SiMe₂-SiMe₂-SiMe₂CI and (CIMe₂Si)₃SiMe to the cleavage reactions of step A),

or wherein methylchloromonosilane MeSiH₂CI is formed by submitting a substrate comprising one or more silanes selected from the group consisting of CI₂MeSi-SiMeCI₂, CbMeSi- SiMe₂CI, CI₂MeSi-SiMe₃, H₂MeSi-SiMeH₂, H₂MeSi-SiMe₂H, H₂MeSi-SiMe₃, HCIMeSi-SiMeH₂, HCIMeSi-SiMeCIH, HCIMeSi-SiMeCI₂, CI₂MeSi-SiMeH₂, CIHMeSi-SiMe₂CI, CI₂MeSi-SiMe₂H, CIHMeSi-SiMe₂H, H₂MeSi-SiMe₂CI, CI₂MeSi-CH₂-SiMeCI₂, CIMe₂Si-CH₂-SiMeCI₂, Me₃Si- CH₂-SiMeCI₂, (CI₂MeSi)₂SiMeCI, (CI₂MeSi)₃SiMe, (CI₂MeSi)₂SiMe-SiCIMe-SiCI₂Me, [(CI₂MeSi)₂SiMe]₂, [(CI₂MeSi)₂SiMe]₂SiCIMe and (CI₂MeSi)₂SiMe-SiMe₂CI to the cleavage reactions of step A),

or wherein methyldichloromonosilane MeSiHCI₂ is formed by submitting a substrate comprising one or more silanes selected from the group consisting of CI₂MeSi-SiMeCI₂, CI₂MeSi-SiMe₂CI, CI₂MeSi-SiMe₃, HCIMeSi-SiMeH₂, HCIMeSi-SiMeCIH, HCIMeSi-SiMeCb, CI₂MeSi-SiMeH₂, CIHMeSi-SiMe₂CI, CI₂MeSi-SiMe₂H, CIHMeSi-SiMe₂H, H₂MeSi-SiMe₂CI, CI₂MeSi-CH₂-SiMeCI₂, CIMe₂Si-CH₂-SiMeCI₂, Me₃Si-CH₂-SiMeCI₂, (CI₂MeSi)₂SiMeCI, (CI₂MeSi)₃SiMe, (CI₂MeSi)₂SiMe-SiCIMe-SiCI₂Me, [(CI₂MeSi)₂SiMe]₂,

[(CI₂MeSi)₂SiMe]₂SiCIMe and (CI₂MeSi)₂SiMe-SiMe₂CI to the cleavage reactions of step A).